Comparison of biohydrogen production efficiency by Rhodopseudomonas palustris MP3 and Rhodopseudomonas harwoodiae SP6 using NO-Fe complex as an enhancement factor

In the present study, nanoscale organic-iron complex (NO-Fe) was used as an enhancement factor by two different Rhodopseudomonas species of purple non sulphur bacteria (PNSB) to produce hydrogen (H2). The NO-Fe complex was synthesised using Eucalyptus viminalis-a native Australian plant leaf extract, and FeSO4.7H2O salt. This NO-Fe complex was used as an iron source for newly isolated Rhodopseudomonas palustris MP3 and Rhodopseudomonas harwoodiae SP6 strains of photo-fermentative bacteria to produce H2. FeSO4.7H2O was also used as a source of iron for comparison with the NO-Fe complex. The photofermentative bacterial cultures were isolated from a fishpond, and only two strains, MP3 and SP6, were found viable after several attempts of quadrate streaking. After phylogenetic analysis, these strains were designated as R. palustris MP3 and R. harwoodiae SP6. The results showed that the R. palustris MP3 strain manifested approximately 70 % higher performance to the NO-Fe complex (FeEx1:2 and FeEx2:1), with an increase in H2 production compared to ferrous salt. The best performance was achieved by both strains when NO-Fe complex FeEx1:2 was supplemented in the fermentation broth at 10 mg/L concentration. The highest production of H2 was observed by R. palustris MP3 (10.7 ml/L) compared to R. harwoodiae SP6 (10 ml/L) when NO-Fe complex FeEx1:2 was used as an iron source. The study revealed that R. palustris MP3 and R. harwoodiae SP6 exhibited higher response to NO-Fe complex FeEx1:2 compared to the control. NO-Fe complex FeEx1:2 was considered highly conductive for efficient H2 production for further research. Citation: Kanwal, F.; Tahir, A.; Tsuzuki, T.; Nisbet, D.; Chen, J.; Torriero, A.A.J. Comparison of Hydrogen Production Efficiency by Rhodopseudomonas palustris MP3 and Rhodopseudomonas harwoodiae SP6 Using an Iron Complex as an Enhancement Factor. Energies 2023, 16, 5018. https://doi.org/10.3390/en16135018